OPC Unified Architecture is a platform-independent standard through which various kinds of systems and devices can communicate by sending messages between clients and servers over various types of networks. OPC is an acronym for “OLE (Object Linking and Embedding) for Process Control”. OPC UA supports robust, secure communication that assures the identity of clients and servers and resists attacks. OPC UA defines sets of services that servers may provide, and individual servers specify to clients what service sets they support. Information is conveyed using OPC UA-defined and vendor-defined data types, and servers define object models that clients can dynamically discover. Servers can provide access to both real-time and historical data to notify clients of important changes. OPC UA can be mapped onto a variety of communication protocols and data can be encoded in various ways to trade off portability and efficiency.
OPC UA provides a consistent, integrated address space and service model. This allows a single OPC UA server to integrate real-time data and historical data into its address space, and to provide access to them using an integrated set of services. These services also include an integrated security model.
In a typical industrial plant using the OPC UA to retrieve and store real-time data from field devices, the data is used to monitor and control processes in that industrial plant. An example of a system 100 is shown in FIG. 1. At least one client 102 is connected to a data server 110. The data server 110 includes, not limited to, modules—a plurality of services 112 to communicate with client 102, and an address space 114.